Patent GB-1019900-A (GB)
Title: Improvements in simultaneous recording and display system
IPC: H01J31/06
Filed: 1963-04-25
Abstract: Electrostatic recording apparatus in which information is recorded as charges on an insulating member and subsequently developed by dusting and similar technique is characterized by the association of an electroluminescent member with the insulating member for the purpose of providing a visual display of the information being recorded.  The invention is described as applied to:  (1) pictorial recording apparatus (see Division H4) in which the insulating recording member and electroluminescent member are located between a row of electrodes controlled by signals and a transparent backing electrode, (2) alpha-numeric printing apparatus (see Division B6) in which the recording and electroluminescent members are located between a cylindrical character-forming electrode and transparent backing electrode, and (3) digital data recording apparatus (see Division B6) where the insulating and electroluminescent members are arranged between orthogonally disposed groups of parallel electrodes so as to permit recording and display at any selected intersection.  The insulating member is in the form of a flexible web which is advanced continuously or intermittently, whilst the electroluminescent member is in the form of a similar flexible web or a stationary plate.  In application (1) and (2) whence a transparent backing electrode is provided this may be a thin coating of tin oxide, copper iodide on a flexible support. Alternatively the conductive electrode may be fixed and separate from the electroluminescent member.  The electroluminescent material may comprise silicon carbide or zinc sulphide activated with small amounts of lead, copper or manganese. Reference is made to the use of an embedding matrix of high dielectric constant, such as polyvinyl chloride, and the use of barium titanate as an additive to raise the average dielectric constant of the whole member.  The matrix may be sufficiently conducting to allow deposited charges to leak away.  Alternatively a substantially non-conductive matrix may be used and the charged removed by contact with a special electrode. Reference is also made to the provision of a thin coating of a conductive anti-static material, such as a quaternary ammonium salt or sodium polyacrylate. The electroluminescent member has a very short persistence.  A long persistence display may be obtained by providing a further electro-luminescent member together with a photo-conductive member located between transparent conductive layers connected to an alternating voltage-supply.  Light from the first electroluminescent layer increases the conductivity of photo-conductor to thereby control the energization of the further electroluminescent member and optical feedback causes the display to persist.  The further electroluminescent member may employ the same materials as the first. The photo-conductive layer may comprise selenium, cadmium sulphide or zinc oxide which is embedded in a fine opaque insulating grid. The further electroluminescent member, photo-conductive member and transparent layers, are constructed as a flexible web.